Agricultural formulation products must be physically and chemically stable for a specified period of time in order to have commercial utility. There are many causes of formulation instabilities, such as active ingredient instability, phase separations and environmental factors (temperature, humidity/moisture, etc.). In today's agrochemical market, it is becoming increasingly common to develop new formulations containing multiple active ingredients and their required solvents, safeners, and/or adjuvants, etc., in order to achieve the optimal spectrum, efficacy and delivery efficiency, which consequently makes formulation stability more and more challenging. Therefore, technologies that can effectively isolate, hinder or eliminate adverse reactions or interactions between incompatible ingredients are often critical for a successful product.
An agrochemical active ingredient, such as a herbicide, insecticide or fungicide or a herbicide safener, can rarely be used in its originally manufactured form. Agrochemical products generally consist of two parts, the active ingredient and the co-formulants or inert ingredients combined together in a formulation. The combination of these two parts into the final product is conducted with two primary goals in mind: (1) maintaining the stability of the product during storage and (2) providing an easy and effective way to use the product upon dilution in a carrier such as water or oil for spray application to an area to be treated.
Agrochemical formulations are generally designed based on customer needs and the physiochemical properties of the active ingredient(s), for example, the solubility of the active ingredient in water and other non-aqueous solvents. There are two major categories of formulations, solid formulations and liquid formulations. Liquid formulations are generally preferred by customers due to their ease of handling in measuring, pumping, diluting and spraying operations.
Oil dispersions (OD) are one type of liquid formulation and are defined as stable suspensions of active ingredients in a water-immiscible fluid which may contain other dissolved active ingredients and is intended for dilution with water before use. Oil dispersion formulations have recently become more important in current formulation research. In addition to customer preferences for liquid formulations, oil dispersion formulations are very suitable for the following scenarios: (1) water sensitive active ingredients, e.g., sulfonylureas which may be susceptible to degradation by hydrolysis, 2) compatibility issues with active ingredient mixtures and 3) the need for build-in adjuvancy.
The basic components of an agricultural oil dispersion formulation are the solvent or oil phase and the dispersed solid phase. These basic components may include active ingredients, petroleum or naturally derived solvents, safeners, rheology modifiers, emulsifiers, dispersants and other co-formulants that help deliver the desired attributes of the product. Rheology modifiers provide physical stability to the formulation by increasing the viscosity of the liquid phase in order to prevent insoluble active ingredient particles from falling out of suspension and forming a layer at the bottom of the storage container. This phenomenon, known as sedimentation, can result in difficulties in the delivery and use of the product if the sediment layer of particles forms a hard pack that is difficult to disperse and re-suspend. A related physical instability of liquid formulations is syneresis. Syneresis in an oil dispersion formulation is generally measured as the amount of top-clearing due to phase separation.
There are a variety of materials, both natural and man-made, that have been used as rheology modifiers to stabilize oil dispersion formulations against sedimentation such as, for example, clays and organoclays, hydrophilic and hydrophobic silicas, hydrogenated castor oils and their derivatives, polyamides, oxidized waxes, associative thickeners, which form structures by themselves due to their limited solubility in solvents, and steric dispersants (e.g., comb polymers such as polyvinylpyrrolidinones or polyacrylates).
It is very common to combine one or more rheology modifiers in a single oil dispersion formulation to obtain the desired rheological properties and, at the same time, minimize any adverse interactions that may occur between ingredients. The proper choice and amounts of oil dispersion rheology modifiers can enhance the thickening efficacy and application range of a particular formulation. Factors to consider in the selection of rheology modifiers in the design of a stable oil dispersion formulation are the type of solvent, the interactions with emulsifiers, the robustness in activation of the thickeners and the temperature sensitivity of the final system.
While there are rheology modifiers available for use in stabilizing agrochemical oil dispersion formulations against particle sedimentation, there is a constant need for new ways to stabilize these formulations owing to limitations with existing choices, incompatibilities with surfactants and active ingredients and the diversity in chemistry of new active ingredients and solvents being discovered and developed today. In addition, the increasing number of active ingredients included in a single formulation can present formulation challenges. These limitations may be overcome by finding new rheology modifiers or additives that act to improve the performance of existing rheology modifiers.
Certain man-made and naturally derived polymers may be used in combination with conventional rheology modifiers such as hydrophilic and hydrophobic silicas, colloidal silicon dioxides, clays, and organoclays to improve the stability of oil dispersion formulations against sedimentation such as those disclosed, for example, in U.S. Pat. No. 5,599,768 and U.S. Pat. No. 6,743,756. In these examples, protic solvents such as alcohols, glycols, water and the like are necessary additives or solvents that are integral to the thickening effect of the rheology system leading to inhibition of particle settling during product storage. However, protic solvents such as water or alcohols may at times be incompatible with some active ingredients and herbicide safeners present in oil dispersion formulations. In particular, in the presence of water some sulfonylurea herbicides have a tendency to hydrolyze via cleavage at the sulfonylurea bridge as described, for example, by J.-P. Carnbon and J. Bastide in, “Hydrolysis Kinetics of Thifensulfuron Methyl in Aqueous Buffer Solutions,” J. Agric. Food Chem., 44, pg. 333-337 (1996). The herbicide safener cloquintocet mexyl is also very prone to hydrate formation upon exposure to water, as disclosed, for example, in WO 02/36566 A1, with subsequent Ostwald Ripening of the resulting hydrate crystals. Because of these and other active ingredient and co-formulant incompatibilities, there is a continued need for new rheology systems that stabilize oil dispersions to particle settling.
The present invention describes agricultural oil dispersion compositions of improved stability containing active ingredients and safeners that can at times be prone to chemical degradation by protic solvents or other active ingredients. It has been found that when polymers or oligomers capable of hydrogen bonding are used in combination with clay or silica type rheology modifiers, in the absence of protic solvents, they provide improved physical stability to oil dispersion formulations of agrochemical products. The present invention provides new compositions of stable oil dispersion formulations of agrochemical products that are suitable in controlling undesired vegetation, insects and plant diseases, the inventive composition consisting essentially of an organic solvent, a dispersed active ingredient, a clay or silica type rheology modifier, a polymer or oligomer capable of hydrogen bonding and at least one surfactant.